The invention relates to an actuator having two outputs for effecting two different, mutually independent setting movements. The two outputs may be connected to two different objects for setting the positions of those two objects independently of each other, but those two outputs may also be connected, at two different locations, with one object for effecting two different setting movements of that one object, for instance two pivotal movements about two different pivotal axes. In particular, the present invention relates to such an actuator having only one motor.
Such an actuator is in particular, but not exclusively, useful in a wing or outside mirror for a motorcar, and will therefore hereinafter be described for such a practical example.
Presently, the various types of wing mirrors are known, in which a mirror plate is adjustably mounted in a mirror housing, the position of that mirror plate being adjustable by a pivotal movement about two substantially perpendicular pivotal axes, which pivotal movements can be remotely performed by the driver from the driver's seat by means of motors likewise mounted in that mirror housing.
In a typical automotive wing mirror application, the mirror plate can be pivoted in four directions: up or down relative to a horizontal pivotal axis, and leftwards or rightwards relative to a vertical pivotal axis. Furthermore, it is known in such applications that the mirror plate can be adjusted from any orientation in any of these four directions, which offers much ease of operation. However, a drawback of such actuators is that they require two motors, each capable of rotating in two directions, one motor operating the up/down displacements and the other motor operating the left/right displacements. These two motors occupy relatively much space in the mirror housing, and render the actuator as a whole relatively expensive. Moreover, for operating these two motors, a likewise relatively expensive five-position switch is needed.
There is a need for an actuator capable of setting a part, such as a mirror plate, in any position, both in horizontal direction and in vertical direction, but whose construction is considerably less expensive. To meet this need, actuators have already been proposed which have only one motor. Such one-motor actuators are based on a cyclic displacement in each of the two freedoms of movement, one freedom of movement (horizontal) being operated by causing the motor to rotate in one direction, while the other freedom of movement (vertical) is operated by causing the motor to rotate in the other direction. Hence, in such actuators, it is not possible to adjust a mirror plate from any orientation in any of the four directions mentioned. With regard to the horizontal freedom of movement, energization of the motor will result in a leftward pivotal movement until the leftmost position is reached; next, the mirror plate will perform a rightward pivotal movement until the rightmost position is reached, whereupon the direction of the pivotal movement is reversed again, and so on, which is referred to as a cyclic movement.
A one-motor actuator therefore comprises first cyclic displacement means for effecting a cyclic movement of the part to be displaced in a first direction, second cyclic displacement means for effecting a cyclic movement of the part to be displaced in a second direction, and separation-transmission means which are coupled between the motor and the first and second cyclic displacement means for driving the first cyclic displacement means when the motor is rotated in one direction, and for driving the second cyclic displacement means when the motor is rotated in the other direction.
German Offenlegungsschrift 4,321,847 describes a one-motor actuator in which a worm mounted on the output shaft of the motor drives two gear wheels. Each gear wheel drives a second worm via a one-direction coupling. Each second worm drives a worm wheel coaxially coupled to a circular disk. A coupling rod to the mirror support plate is eccentrically mounted on the circular disk.
This known actuator has a relatively large number of parts. Further, this known actuator has the drawback that the motor must at all times drive two gear wheels which are both provided with a one-direction coupling, as a consequence of which the known actuator has a relatively low efficiency. Further, in this known actuator, the one-direction couplings are loaded rather heavily.
In particular when used in a motor vehicle wing mirror, it is desired that the mirror plate can also be adjusted manually by exerting an external force, for instance in the event of a defect to the electric operating mechanism. For that purpose, the coupling rod of the known actuator is of a two-piece construction, the first bar-shaped part being capable of pivoting telescopically in the second part, which is substantially constructed as a hollow cylinder. The first bar-shaped part has its outer surface provided with ribs, and the second hollow cylindrical part has its inner surface provided with springing projections cooperating these ribs. When an external force is exerted, these projections move across these ribs, causing the axial length of the coupling bar to change.
Two major drawbacks are inherent in this construction. Firstly, it is not possible to retrieve the original position with certainty by exerting an external force in opposite direction. Secondly, it is not possible to undo the manual change, i.e., the changed axial length of the coupling bar, by a subsequent electric adjustment, which means that after a manual adjustment, the adjusting range of the actuator has changed.
Another example of a one-motor actuator is described in U.S. Pat. No. 4,474,428 in which a speed-reducing mechanism is arranged, in alignment with the motor shaft. In such an arrangement two drive disks are eccentrically mounted concentrically with the driven shaft of the speed-reducing mechanism, each drive disk being coupled to an output of an axial two-way coupling. One of those drive disks is disposed without play in a fork construction which is mounted with a bearing in the mirror housing for a linear movement, while the other one of those drive disks is surrounded without play by a ring which is connected, via a curved bar, to the mirror support plate. This known construction, also, has a number of drawbacks. Important disadvantages of this known construction are that the construction is fairly complicated and requires much space; and, the mirror cannot be adjusted manually.